Well as much as I think I'd like to see Rose again - I agree her arc was pretty well wrapped up. But then again... she was still the first modern series companion. And she does have a Doctor of her own with a baby Tardis too - so it's feasible that they could crop up somehow.
I'd even think it'd be interesting if somehow there was some massive anomaly that basically somehow, 11 encounters a lot of his previous selves or their companions. Doesn't even have to be some 'BIIIIIG' story - could be wrapped up in a two parter or a special. I'm sure there's got to be some English or American or Aussie actors that can 'resemble' any of the previous Doctors long enough for a quick cameo. Heck, I'd even be happy if he just reverted to each of his previous incarnations during the story and then shoot forward back to 11.
Even if we dont' see companions - or maybe only briefly. Heck they could even repurpose some old footage, just remaster it and clean it up so it fits better and it could be a fitting 50th anniversary tribute and only takes one or two episodes to resolve. Could even be sold/packaged as a special unto itself.